Selective deficit of auditory localisation in patients with visuospatial neglect.

Possible auditory deficits in neglect were examined by comparing the performance of four right brain-damaged (RBD) patients with left visuospatial neglect, versus four RBD patients without neglect, in three auditory tasks. The first task required speeded discrimination of sound elevation, by moving a central lever up or down according to the vertical position of a peripheral target sound, regardless of its side. The other two auditory tasks were non-spatial, requiring either speeded pitch discrimination (moving the central lever up for high pitch, down for low pitch) or speeded target detection. Neglect patients' performance was impaired with respect to RBD controls only when the auditory task required spatial coding of the target sound (the up/down spatial discrimination). This demonstrates a selective deficit of auditory space perception in neglect patients. This auditory spatial deficit was more pronounced for left than right sounds. Since auditory space perception was impaired in the vertical dimension, the observed deficit cannot be attributed to a systematic rightward shift in sound localisation. Instead, the results suggest increased spatial uncertainty in sound localisation by neglect patients, particularly for auditory targets on the contralesional side. These findings are related to multimodal coding of space in the parietal cortex, which was damaged in the neglect patients, but not in the RBD controls.